JP6844269B2 - Liquid discharge device - Google Patents

Description

The present invention relates to a liquid discharge device including a transport unit for transporting a recording medium and a discharge unit having a plurality of discharge ports for discharging liquid to the recording medium.

In Patent Document 1 (FIG. 2), a transport roller pair (upstream roller pair) arranged upstream of the transport path with respect to the recording head (discharge unit) and a transport roller pair (upstream roller pair) arranged downstream of the transport path with respect to the recording head. An image recording device including a paper ejection roller pair (first downstream roller pair) and a switchback roller pair (second downstream roller pair) arranged downstream of the paper ejection roller pair. Is disclosed. The surface rollers that come into contact with the surface of the recording medium (the surface on which the liquid is discharged) in the paper ejection roller pair and the switchback roller pair are spur rollers having one or more protrusions formed on the outer peripheral surface. As a result, it is possible to suppress the transfer of the liquid that has landed on the surface of the recording medium to the surface roller.

Japanese Unexamined Patent Publication No. 2011-245835

In the configuration in which the recording medium is conveyed using three roller pairs (upstream roller pair, first downstream roller pair, and second downstream roller pair) as described above, the rear end of the recording medium passes through the upstream roller pair and the discharge portion. When the recording medium is conveyed between the first downstream roller pair and the second downstream roller pair without passing through the discharge area (below the recording head), the first downstream roller pair and the first downstream roller pair are used to maintain the recording quality. It is necessary to stabilize the transfer by providing a difference in the rotation speed and the transfer force (particularly, the holding force of the recording medium between the front surface roller and the back surface roller) between the second downstream roller pair. Specifically, the rotation speed of the second downstream roller pair is made larger than the rotation speed of the first downstream roller pair, and the conveying force of the first downstream roller pair is larger than the conveying force of the second downstream roller pair. Make it large enough (for example, about 10 times). As a result, the recording medium slips on the second downstream roller pair, and the first downstream roller pair mainly performs the transfer, so that the transfer can be stabilized.

As described above, the transport force of the first downstream roller pair needs to be sufficiently larger than the transport force of the second downstream roller pair from the viewpoint of maintaining the recording quality, but the recording medium is damaged by the pressing of the protrusions. From the viewpoint of prevention, it is preferable not to make it too large. On the other hand, if the conveying force of the second downstream roller pair is made too small, when the recording medium is conveyed only by the second downstream roller pair, the recording medium may slip and the conveying may not be possible. Therefore, it is difficult to make the transport force of the first downstream roller pair sufficiently larger than the transport force of the second downstream roller pair, and when the recording medium is conveyed between the first downstream roller pair and the second downstream roller pair. In addition, the transport is not stable and the recording medium may be skewed.

An object of the present invention is to discharge a liquid capable of stabilizing the transfer and preventing skewing when the recording medium is conveyed between the first downstream roller pair and the second downstream roller pair whose surface rollers are spur rollers. To provide the equipment.

The liquid discharge device according to the first aspect of the present invention has a transport unit that transports the recording medium along the transport path, and a plurality of discharge ports that discharge the liquid on the surface of the recording medium transported by the transport unit. The transport section includes an upstream roller pair arranged upstream of the transport path with respect to the discharge section, and a first downstream roller arranged downstream of the transport path with respect to the discharge section. Each of the upstream roller pair, the first downstream roller pair, and the second downstream roller pair includes a pair and a second downstream roller pair arranged downstream of the transport path with respect to the first downstream roller pair. The recording medium is conveyed by aligning the axial center of the recording medium with the axial center of the recording medium, and the upstream roller pair, the first downstream roller pair, and the second downstream roller pair are recorded. It has a front surface roller that contacts the front surface of the medium and a back surface roller that contacts the back surface of the recording medium opposite to the front surface, and the front surface roller and the back surface roller hold the recording medium in opposite directions. The surface rollers of the first downstream roller pair and the second downstream roller pair are configured to transfer the recording medium by applying a conveying force to the recording medium by rotating to 1. It is a accelerating roller on which the above protrusions are formed, the rotational speed of the second downstream roller pair is larger than the rotational speed of the first downstream roller pair, and the conveying force of the first downstream roller pair is The surface roller of the second downstream roller pair, which is larger than the carrying force of the second downstream roller pair, includes a plurality of second partial rollers separated from each other in the axial direction, and among the plurality of second partial rollers. The friction coefficient of the outer peripheral surface of the second partial roller arranged at the position closest to the center in the axial direction is larger than the friction coefficient of the outer peripheral surface of the other second partial roller, and the friction coefficient of the second downstream roller pair The carrying force is not constant in the axial direction of the roller pair, but is greatest at a position closest to the axial center of the roller pair.
The liquid discharge device according to the second aspect of the present invention has a transport unit that transports the recording medium along the transport path, and a plurality of discharge ports that discharge the liquid on the surface of the recording medium conveyed by the transport unit. The transport section includes an upstream roller pair arranged upstream of the transport path with respect to the discharge section, and a first downstream roller arranged downstream of the transport path with respect to the discharge section. Each of the upstream roller pair, the first downstream roller pair, and the second downstream roller pair includes a pair and a second downstream roller pair arranged downstream of the transport path with respect to the first downstream roller pair. The recording medium is conveyed by aligning the axial center of the recording medium with the axial center of the recording medium, and the upstream roller pair, the first downstream roller pair, and the second downstream roller pair are recorded. It has a front surface roller that contacts the front surface of the medium and a back surface roller that contacts the back surface of the recording medium opposite to the front surface, and the front surface roller and the back surface roller hold the recording medium in opposite directions. The surface rollers of the first downstream roller pair and the second downstream roller pair are configured to transfer the recording medium by applying a conveying force to the recording medium by rotating to 1. It is a accelerating roller on which the above protrusions are formed, the rotational speed of the second downstream roller pair is larger than the rotational speed of the first downstream roller pair, and the conveying force of the first downstream roller pair is The surface roller of the second downstream roller pair, which is larger than the carrying force of the second downstream roller pair, includes a plurality of second partial rollers separated from each other in the axial direction, and each of the plurality of second partial rollers. Is further provided with a plurality of urging members for imparting urging forces toward the back surface roller, and among the plurality of urging members, the plurality of second partial rollers are arranged at positions closest to the center in the axial direction. The urging member provided for the second partial roller is larger than the remaining urging member, and the conveying force of the second downstream roller pair is the axial direction of the roller pair. It is characterized in that it is not constant and is the largest at the position closest to the center of the roller pair in the axial direction.

According to the present invention, the rotation speed of the second downstream roller pair is larger than the rotation speed of the first downstream roller pair, and the transport force of the first downstream roller pair is larger than the transport force of the second downstream roller pair. large. Then, under this condition, the transport force of the second downstream roller pair is not constant in the axial direction, but is maximized at the position closest to the center in the axial direction. As a result, when the recording medium is conveyed between the first downstream roller pair and the second downstream roller pair whose surface rollers are spur rollers, the transfer can be stabilized and skewing can be prevented. Specifically, by making the transport force of the second downstream roller pair the largest at the position closest to the center in the axial direction without making it constant in the axial direction, the transport force of the first downstream roller pair may be made too large. 2. The transport force of the first downstream roller pair can be made sufficiently larger than the transport force of the second downstream roller pair without making the transport force of the two downstream roller pairs too small. As a result, the transport force of the first downstream roller pair is made too large, which causes damage to the recording medium due to the pressing of the protrusions, and the transport force of the second downstream roller pair is made too small, so that the second downstream roller is used. When the recording media are conveyed only in pairs, the problem that the recording media slips and cannot be conveyed can be suppressed, the transfer can be stabilized, and skewing can be prevented.
Further, according to the present invention, the surface rollers of the second downstream roller pair include a plurality of second partial rollers separated from each other in the axial direction. In this case, it is easy to change the transport force of the second downstream roller pair in the axial direction by adjusting the configuration of each second partial roller and the urging force of the urging member provided for each second partial roller. Therefore, it is possible to easily realize a configuration in which the transport force of the second downstream roller pair is the largest at the position closest to the center in the axial direction.
Further, according to the first aspect of the present invention, the friction coefficient of the outer peripheral surface of the second portion roller arranged at the position closest to the center in the axial direction among the plurality of second portion rollers is the other second portion. It is larger than the coefficient of friction of the outer peripheral surface of the roller. In this case, by adjusting the friction coefficient of the outer peripheral surface of the second partial roller, it is possible to easily realize a configuration in which the transport force of the second downstream roller pair is the largest at the position closest to the center in the axial direction.
Further, according to the second aspect of the present invention, among the plurality of urging members for applying the urging force toward the back surface roller to each of the plurality of second partial rollers, the center of the plurality of second partial rollers in the axial direction. The urging member provided for the second partial roller arranged at the position closest to the urging member has a larger urging force than the remaining urging member. In this case, by adjusting the urging force of the urging member, it is possible to easily realize a configuration in which the conveying force of the second downstream roller pair is the largest at the position closest to the center in the axial direction.

The transport unit is configured to be capable of transporting recording media of a plurality of sizes, and the distance from the upstream roller pair to the second downstream roller pair along the transport path is one of the plurality of sizes. The size of the recording medium may be less than or equal to the length along the transport path. In this case, the second downstream roller pair sandwiches the recording medium before the rear end of the recording medium passes through the upstream roller pair, and the recording medium is not conveyed only by the first downstream roller pair. Therefore, it is possible to suppress a problem that may occur when the recording medium is conveyed only by the first downstream roller pair (the problem that the posture of the recording medium tends to be unstable).

The surface roller of the first downstream roller pair may include a plurality of first partial rollers separated from each other in the axial direction. In this case, while the transfer of the liquid landing on the surface of the recording medium to the surface roller can be more reliably suppressed, there are a plurality of liquids due to the manufacturing error of the first partial roller and the configuration of the urging member provided for each first partial roller. In the first partial roller of the above, the friction coefficient of the outer peripheral surface and the pressing force against the back surface roller are likely to vary. Therefore, the transport force of the first downstream roller pair tends to vary in the axial direction, and when the recording medium is transported between the first downstream roller pair and the second downstream roller pair, the transport becomes unstable and skewing occurs. Although it is likely to occur, in the present invention, it is possible to stabilize the transport and prevent skewing.

The liquid discharge device according to the present invention may satisfy the following formulas (1) and (2). In this case, skewing can be more reliably prevented when the recording medium is conveyed between the first downstream roller pair and the second downstream roller pair whose surface rollers are spur rollers.
| M1 |> | M2 | (1)
| M1 | / L1 <∫F2 (l) ・ dl (2)
(Here, M1: the moment around the center of the first downstream roller pair in the axial direction caused by the variation in the carrying force of the first downstream roller pair in the axial direction, M2: the said of the second downstream roller pair. Moment around the center of the second downstream roller pair caused by the variation in the transport force in the axial direction, L1: Distance from the first downstream roller pair to the second downstream roller pair along the transport path. , F2 (l): The transport force at each point l in the axial direction of the second downstream roller pair)

The liquid discharge device according to the present invention may further satisfy the following formulas (3) and (4). In this case, skewing can be prevented even when the recording medium is conveyed between the upstream roller pair and the first downstream roller pair.
｜ M0 ｜＞｜ M1 ｜ (3)
| M0 | / L2 <∫F1 (l) ・ dl (4)
(Here, M0: a moment around the center of the upstream roller pair in the axial direction caused by the variation in the carrying force of the upstream roller pair in the axial direction, L2: from the upstream roller pair to the first downstream roller pair. Distance along the transport path, F1 (l): the transport force at each point l in the axial direction of the first downstream roller pair)

The rotational speed of the first downstream roller pair may be larger than the rotational speed of the upstream roller pair, and the conveying force of the upstream roller pair may be larger than the conveying force of the first downstream roller pair. In this case, even when the recording medium is conveyed between the upstream roller pair and the first downstream roller pair, the transfer can be stabilized.

The second downstream roller pair may be a roller pair arranged most downstream of the transport path. In this case, even if skew occurs when the recording medium is conveyed only by the second downstream roller pair, defects (jams, etc.) due to skew can be suppressed.

The second downstream roller pair may have a function of imparting a wave shape along the axial direction to the recording medium. In this case, from the viewpoint of imparting a wave shape to the entire width of the recording medium, it is preferable to arrange the second downstream roller pair over the entire width of the recording medium, but the conveying force of the second downstream roller pair should be constant in the axial direction. By making it the largest at the position closest to the center in the axial direction, when the recording medium is conveyed between the first downstream roller pair and the second downstream roller pair whose surface rollers are accelerating rollers, the transfer is stabilized. It is possible to prevent skewing.

The first outermost position of the second downstream roller pair from the center in the axial direction is higher than the first outermost position where the first downstream roller pair sandwiches the recording medium farthest from the center in the axial direction. The second outermost position that sandwiches the recording medium farthest in the same direction as the above may be located closer to the center in the axial direction. In this case, when the recording medium is conveyed by the first downstream roller pair and the second downstream roller pair whose surface rollers are spur rollers, it becomes easy to satisfy the requirements for stabilizing the transfer and preventing skewing.

The conveying force of the second downstream roller pair may be the smallest at the position farthest from the center in the axial direction of the roller pair. In this case, by making the transport force of the second downstream roller pair the largest at the position closest to the center in the axial direction and the smallest at the position farthest from the center in the axial direction, the first downstream where the surface roller is a spur roller. When the recording medium is conveyed by the roller pair and the second downstream roller pair, it is possible to more reliably realize the stabilization of the transfer and the prevention of skewing.

According to the present invention, the rotation speed of the second downstream roller pair is larger than the rotation speed of the first downstream roller pair, and the transport force of the first downstream roller pair is larger than the transport force of the second downstream roller pair. large. Then, under this condition, the transport force of the second downstream roller pair is not constant in the axial direction, but is maximized at the position closest to the center in the axial direction. As a result, when the recording medium is conveyed between the first downstream roller pair and the second downstream roller pair whose surface rollers are spur rollers, the transfer can be stabilized and skewing can be prevented.

It is sectional drawing along the vertical direction which shows the inside of the printer which concerns on one Embodiment of this invention. It is a partial cross-sectional view of the ejection part in the printer which concerns on one Embodiment of this invention. It is a top view which shows the roller pair and the discharge part of the transport part in the printer which concerns on one Embodiment of this invention. FIG. 3 is a view seen from the direction of arrow IV in FIG. It is a schematic diagram which shows the relationship between the transport force and the moment of each roller pair.

<Overall configuration>
As shown in FIG. 1, the printer 1 according to an embodiment of the present invention includes a paper feed tray 10 capable of loading and accommodating a plurality of paper 100 and a plurality of paper 100 housed in the paper feed tray 10. A discharge unit 30 having a transport unit 20 that transports the uppermost layer of paper 100 along the transport path R, and a plurality of discharge ports 30x (see FIG. 2) that discharge ink onto the surface of the paper 100 that is conveyed by the transport unit 20. A platen 40 facing a discharge surface 30a having a plurality of discharge ports 30x opened in the discharge unit 30, and a paper discharge tray 50 for receiving the paper 100 conveyed by the transfer unit 20 are included.

<Discharge section>
As shown in FIG. 2, the discharge unit 30 includes a flow path unit 30 m and an actuator unit 30 n.

The lower surface of the flow path unit 30 m corresponds to the discharge surface 30a. Inside the flow path unit 30m, a common flow path 30y communicating with an ink tank (not shown) and an individual flow path 30z for each discharge port 30x are formed. The individual flow path 30z is a flow path from the outlet of the common flow path 30y to the discharge port 30x via the pressure chamber 30z1. A plurality of pressure chambers 30z1 are opened on the upper surface of the flow path unit 30m.

The actuator units 30n are a plurality of diaphragms 30n1 arranged on the upper surface of the flow path unit 30m so as to cover the plurality of pressure chambers 30z1, a piezoelectric layer 30n2 arranged on the upper surface of the diaphragm 30n1, and a plurality of piezoelectric layers 30n2 on the upper surface of the piezoelectric layer 30n2. It includes a plurality of individual electrodes 30n3 arranged so as to face each of the pressure chambers 30z1 of the above. The portion of the diaphragm 30n1 and the piezoelectric layer 30n2 sandwiched between each individual electrode 30n3 and each pressure chamber 30z1 functions as an individual unimorph type actuator for each pressure chamber 30z1, and the voltage to each individual electrode 30n3 by the head driver 30d. Can be deformed independently according to the application of. By deforming the actuator so as to be convex toward the pressure chamber 30z1, the volume of the pressure chamber 30z1 is reduced, pressure is applied to the ink in the pressure chamber 30z1, and the ink is discharged from the discharge port 30x.

The ejection unit 30 is a serial type, and ejects ink from each ejection port 30x while reciprocating in the scanning direction while being held by a carriage (not shown).

<Transport route>
As shown in FIG. 1, the transport path R is a path R1 from the paper feed tray 10 to the paper output tray 50, a position A defined downstream of the path R1 with respect to the discharge unit 30, and a discharge unit 30. Includes a path R2 that connects to a position B defined upstream of the path R1.

<Transport section>
The transport unit 20 includes a paper feed roller 11 arranged so as to come into contact with the uppermost paper 100 among the plurality of paper 100 housed in the paper feed tray 10, and a discharge unit downstream of the path R1 with respect to the position B. A pair of rollers 21 arranged upstream of the path R1 with respect to 30, a pair of rollers 22 arranged downstream of the path R1 with respect to the discharge unit 30 and upstream of the path R1 with respect to the position A, and with respect to the position A. It includes a roller pair 23 arranged downstream of the path R1, a roller pair 24 arranged on the path R2, and a guide plate 20 g defining the transport path R. The roller pair 23 is arranged at the most downstream side of the transport path R.

When single-sided recording is performed, the paper 100 is conveyed from the paper feed tray 10 along the path R1, and ink is ejected to one side (the side facing downward in the paper feed tray 10) to perform recording. Later, it is received in the output tray 50.

When double-sided recording is performed, the paper 100 is conveyed from the paper feed tray 10 along the path R1, ink is ejected to one side to perform recording, and then the rear end is sandwiched between the rollers and 23. It is temporarily stopped in the state. After that, the paper 100 is conveyed along the path R2 by reversing the conveying direction by rotating the roller pair 23 in the opposite direction, and is returned from the position B to the path R1. Then, the paper 100 is conveyed again along the path R1, ink is ejected to the other surface (the surface facing upward in the paper feed tray 10), recording is performed, and then the paper 100 is received by the paper output tray 50. ..

The roller pairs 21 to 23 are the surface rollers 21a to 23a that come into contact with the surface of the paper 100 (the surface that faces the ejection portion 30 when the paper 100 passes between the ejection portion 30 and the platen 40), and the paper 100. The back surface rollers 21b to 23b are in contact with the back surface opposite to the front surface of the paper, and the front surface rollers 21a to 23a and the back surface rollers 21b to 23b rotate in opposite directions while sandwiching the paper 100. It is configured to apply a conveying force to 100 to convey the paper 100.

Of the roller pairs 21 to 23, the roller pair located downstream of the path R1 has a higher rotation speed. That is, the rotation speed of the roller vs. 23 is larger than the rotation speed of the roller vs. 22, and the rotation speed of the roller vs. 22 is larger than the rotation speed of the roller vs. 21. Thereby, the transportation can be stabilized.

Of the roller pairs 21 to 23, the roller pair located upstream of the path R1 has a larger carrying force. That is, the transport force of the roller vs. 21 is larger than the transport force of the roller vs. 22, and the transport force of the roller vs. 22 is larger than the transport force of the roller vs. 23. The conveying force is expressed by the product of the friction coefficient of the outer peripheral surfaces of the front surface rollers 21a to 23a and the back surface rollers 21b to 23b and the holding force of the paper 100 between the front surface rollers 21a to 23a and the back surface rollers 21b to 23b. Can be done.

The transport unit 20 can transport paper 100 of a plurality of sizes, and as shown in FIG. 3, the paper 100 is located at the centers C0 to C2 of each roller pair 21 to 23 in the axial direction (direction parallel to the scanning direction). The center O in the width direction (direction parallel to the axial direction of the roller pairs 21 to 23) is aligned with each other to convey the paper 100. In FIG. 3, the shafts that support the rollers of 21 to 23 for each roller are not shown.

The distance L along the transport path R from the roller pair 21 to the roller pair 23 is the size of one of the plurality of sizes of the paper 100 that can be transported by the transport unit 20 (for example, the most frequently used size (for example). The length of the paper (A4 size, letter size, etc.) along the transport path R of 100 or less.

The front surface roller 21a and the back surface roller 21b of the roller pair 21 are composed of one roller elongated in the axial direction. The front surface rollers 22a, 23a and the back surface rollers 22b, 23b of the roller pairs 22 and 23 are composed of a plurality of partial rollers separated from each other in the axial direction.

The roller pair 22 has eight sets of partial rollers 22a1, 22b1 arranged so as to be in contact with each other. The roller pair 23 has six sets of partial rollers 23a1, 23b1 arranged so as to be in contact with each other. The eight sets of partial rollers 22a1,22b1 and the six sets of partial rollers 23a1,23b1 are arranged at equal intervals in the scanning direction, respectively. The six sets of partial rollers 23a1,23b1 have the same positions in the scanning direction as each of the six sets of partial rollers 22a1,22b1 except for the two sets outside the eight sets of partial rollers 22a1,22b1 in the scanning direction. In the roller pair 22, the positions P1x and P1y where the two sets of partial rollers 22a1, 22b1 located outside in the scanning direction are arranged have the same distance D1 from the center C2 in the scanning direction. In the roller pair 23, the positions P2x and P2y where the two sets of partial rollers 23a1, 23b1 located outside in the scanning direction are arranged have the same distance D2 from the center C2 in the scanning direction. The position P2x is closer to the centers C1 and C2 in the scanning direction than the position P1x, and the position P2y is closer to the centers C1 and C2 in the scanning direction than the position P1y.

As shown in FIG. 1, the partial rollers 22b1, 23b1 of the back surface rollers 22b and 23b are rubber rollers having no protrusions formed on the outer peripheral surface. The partial rollers 22a1, 23a1 of the surface rollers 22a and 23a are spur rollers having one or more protrusions 22ap and 23ap formed on the outer peripheral surface.

<Give wave shape>
As shown in FIGS. 1 and 3, nine corrugated plates 21c are provided above the surface rollers 21a of the roller pair 21 to give the paper 100 a wave shape along the scanning direction, and the surface of the platen 40 (discharge). Eight ribs 40c are provided on the surface facing the portion 30), and seven corrugated spurs 23c are provided immediately downstream of the path R1 with respect to the roller pair 23. By imparting a wavy shape along the scanning direction to the paper 100, it is possible to give the paper 100 a waist and realize good transport.

As shown in FIG. 3, the nine corrugated plates 21c are arranged at equal intervals in the scanning direction. As shown in FIG. 1, each corrugated plate 21c extends from above the surface roller 21a to the downstream of the path R1, and its tip portion faces the surface of the platen 40 with a slight gap.

As shown in FIG. 3, the eight ribs 40c are arranged at equal intervals in the scanning direction and are arranged between the corrugated plates 21c adjacent to each other in the scanning direction. Each rib 40c extends in the transport direction. The positions of the eight ribs 40c coincide with those of the eight sets of partial rollers 22a1,22b1 in the scanning direction.

The tip of each rib 40c is located above the tip of each corrugated plate 21c. In such a positional relationship, the tips of the eight ribs 40c support the paper 100 from below, and the tips of the nine corrugated plates 21c hold the paper 100 from above, so that the paper 100 is aligned with the scanning direction. A wave shape is given.

The seven corrugated spurs 23c are arranged at equal intervals in the scanning direction, and the positions in the scanning direction coincide with each of the seven corrugated plates 14 except for the two outside the scanning direction among the nine corrugated plates 14. A set of partial rollers 23a1, 23b1 is arranged between two corrugated spurs 23c adjacent to each other in the scanning direction.

As shown in FIG. 4, the contact points (points that sandwich the paper 100) of the partial rollers 23a1, 23b1 of each set are located above the lower end of each corrugated spur 23c. In such a positional relationship, the six partial rollers 23b1 support the paper 100 from below, and the seven corrugated spurs 23c hold the paper 100 from above, thereby imparting a wave shape along the scanning direction to the paper 100. To. As described above, the roller pair 23 has a function of imparting a wave shape along the scanning direction to the paper 100 by arranging the corrugated spurs 23c between the sets of the partial rollers 23a1, 23b1.

The force with which the corrugated spur 23c presses the paper 100 is smaller than the force with which the corrugated plate 21c presses the paper 100. Conveying force may also be generated in the portions of the corrugated plate 21c and the corrugated spur 23c, but since the corrugated plate 21c and the corrugated spur 23c are not configured to sandwich the paper 100 with the members below them, they can be ignored.

<Support configuration of each roller>
The seven corrugated spurs 23c are fixed to one shaft 23cx that is long in the scanning direction. The six partial rollers 23b1 of the back surface roller 23b are fixed to one shaft 23bx that is long in the scanning direction. The shafts 23bx and 23cx are rotatably supported by a housing (not shown) of the printer 1.

The six partial rollers 23a1 of the surface roller 23a are fixed to each of the six shafts 23ax that are short in the scanning direction. Each shaft 23ax is rotatably supported by a holder 23ah. On the upper surface of each holder 23ah, a protruding portion 23ay projecting upward from the upper surface is provided. Each protrusion 23ay is inserted into a through hole formed in the plate 1p, and includes a lower portion below the plate 1p and an upper portion above the plate 1p. The plate 1p is fixed to the housing of the printer 1. A spring 23as is wound around the lower portion of each protrusion 23ay, and the holder 23ah is urged downward by the urging force of the spring 23as. That is, each spring 23as applies a urging force toward each partial roller 23b1 of the back surface roller 23b to each partial roller 23a1 of the front surface roller 23a.

Of the six springs 23as, the spring 23as located closer to the center C2 in the scanning direction has a larger urging force. That is, of the six springs 23as, the urging force of the two springs 23as closest to the center C2 in the scanning direction is the largest (the urging force = "large"), and the position farthest from the center C2 in the scanning direction ( The two springs 23as on the outside in the scanning direction have the smallest urging force (the urging force = "small"), and the second spring from the outside in the scanning direction (the spring 23as with the urging force "large" and the spring with the urging force "small"). The urging force of the spring 23as (arranged between the 23as) is "medium". Further, the friction coefficient of the outer peripheral surface of the two partial rollers 23a1 located closest to the center C2 in the scanning direction among the six partial rollers 23a1 is such that the material constituting the outer peripheral surface and the processing of the outer peripheral surface are changed. Therefore, it is larger than the friction coefficient of the outer peripheral surface of the other partial roller 23a1. Due to such a difference in urging force and friction coefficient, the carrying force of the roller pair 23 is not constant in the axial direction, and is the largest at the position closest to the center C2 and the smallest at the position farthest from the center C2. ..

Although not shown, the eight partial rollers 22b1 of the back surface roller 22b of the roller pair 22 are long in the scanning direction and are in the housing of the printer 1 like the six partial rollers 23b1 of the back surface roller 23b of the roller pair 23. It is fixed to a single shaft that is rotatably supported. The eight partial rollers 22a1 of the surface roller 22a of the roller pair 22 are fixed to each of the eight partial rollers 23a1 of the surface roller 23a of the roller pair 23, which are short in the scanning direction, and are fixed to the printer via the holder. It is supported by a plate fixed to the housing of No. 1 and is urged downward (in the direction toward each partial roller 22b1) by the urging force of the spring. The urging forces of the springs provided on the eight partial rollers 22a1 are substantially the same as each other.

The front roller 21a and the back roller 21b of the roller pair 21 are fixed to shafts that are long in the scanning direction and rotatably supported by the housing of the printer 1.

<Relationship between transport force and moment>
The printer 1 is configured to satisfy the following equations (1) to (4) by the configuration and arrangement of each roller pair 21 to 23 as described above (see FIGS. 4 and 5).
| M1 |> | M2 | (1)
| M1 | / L1 <∫F2 (l) ・ dl (2)
｜ M0 ｜＞｜ M1 ｜ (3)
| M0 | / L2 <∫F1 (l) ・ dl (4)
(Here, M1: the moment around the center C1 caused by the variation in the transport force F1 of the roller vs. 22 in the axial direction, M2: the moment around the center C2 caused by the variation in the transport force F2 of the roller pair 23 in the axial direction, L1: The distance along the path R1 from the roller vs. 22 to the roller vs. 23, F2 (l): the transport force at each point l in the axial direction of the roller vs. 23, and M0: the transport force of the roller vs. 21 due to the variation in the axial direction of F0. The generated moment around the center C0, L2: the distance along the path R1 from the roller pair 21 to the roller pair 22, F1 (l): the transport force at each point l in the axial direction of the roller pair 22)
In FIG. 5, F0 (l) indicates the conveying force at each point l in the axial direction of the roller pair 21.

In the present embodiment, since each of the roller pairs 22 and 23 is composed of a plurality of partial rollers separated from each other in the axial direction, the above equations (2) and (4) are replaced with the following equations (2'), respectively. It can be replaced with (4').
| M1 | / L1 <ΣF2'(2')
| M0 | / L2 <ΣF1'(4')
(Here, F2': transport force by each partial roller of roller vs. 23, F1': transport force by each partial roller of roller vs. 22)

As described above, according to the present embodiment, the rotation speed of the roller vs. 23 is larger than the rotation speed of the roller vs. 22, and the transport force of the roller vs. 22 is larger than the transport force of the roller vs. 23. large. Then, under this condition, the transport force F2 of the roller pair 23 is not constant in the axial direction, but is maximized at the position closest to the center C2. As a result, when the paper 100 is conveyed by the roller pairs 22 and 23 in which the surface roller is a spur roller, the transfer can be stabilized and the skewing of the paper 100 can be prevented. Specifically, by making the transport force F2 of the roller pair 23 not constant in the axial direction and making it the largest at the position closest to the center C2 in the axial direction, the transport force F1 of the roller pair 22 can be made too large, or the roller pair can be paired. The transport force F1 of the roller vs. 22 can be sufficiently larger than the transport force F2 of the roller vs. 23 without making the transport force F2 of the roller 23 too small. As a result, there is a problem that the paper 100 is damaged by pressing the protrusion 22ap by making the transport force F1 of the roller vs. 22 too large, and the transport force F2 of the roller vs. 23 is made too small, so that only the roller pair 23 is used. When the paper 100 is conveyed, the problem that the paper 100 slips and cannot be conveyed can be suppressed, the transfer can be stabilized, and skewing can be prevented.

The distance L along the transport path R from the roller pair 21 to the roller pair 23 is the size of one of the plurality of sizes of the paper 100 that can be transported by the transport unit 20 (for example, the most frequently used size (for example). The length of the paper (A4 size, letter size, etc.) along the transport path R of 100 (see FIG. 3). In this case, the roller vs. 23 sandwiches the paper 100 before the rear end of the paper 100 passes through the roller pair 21, and the paper 100 is not conveyed only by the roller pair 22. Therefore, it is possible to suppress a problem that may occur when the paper 100 is conveyed only by the roller pair 22 (the problem that the posture of the paper 100 tends to be unstable).

The surface roller 22a of the roller pair 22 includes eight partial rollers 22a1 that are axially separated from each other (see FIG. 3). In this case, the transfer of the ink that has landed on the surface of the paper 100 to the surface roller 22a can be more reliably suppressed, but due to the manufacturing error of the partial roller 22a1 and the configuration of the spring provided for each partial roller 22a1, eight partial rollers In 22a1, the coefficient of friction on the outer peripheral surface and the pressing force on the back surface roller 22b tend to vary. Therefore, the transport force F1 of the rollers vs. 22 tends to vary in the axial direction, and when the paper 100 is conveyed by the rollers vs. 22 and 23, the transport becomes unstable and skews tend to occur. Then, it is possible to stabilize the transportation and prevent skewing.

The surface roller 23a of the roller pair 23 includes six partial rollers 23a1 that are axially separated from each other (see FIG. 3). In this case, by adjusting the configuration of each partial roller 23a1 and the urging force of the spring 23as provided for each partial roller 23a1, it is easy to change the transport force F2 of the roller pair 23 in the axial direction, and the roller pair It is possible to easily realize a configuration in which the transport force F2 of 23 is the largest at the position closest to the center C2.

Of the six partial rollers 23a1, the friction coefficient of the outer peripheral surface of the two partial rollers 23a1 arranged at the position closest to the center C2 in the axial direction is larger than the friction coefficient of the outer peripheral surface of the other partial rollers 23a1. In this case, by adjusting the friction coefficient of the outer peripheral surface of the partial roller 23a1, it is possible to easily realize a configuration in which the transport force F2 of the roller pair 23 is the largest at the position closest to the center C2 in the axial direction.

Of the six springs 23as, the springs 23as provided for the two partial rollers 23a1 arranged at the positions closest to the center C2 in the axial direction among the six partial rollers 23a1 are attached more than the remaining springs 23as. The power is large (see Fig. 4). In this case, by adjusting the urging force of the spring 23as, it is possible to easily realize a configuration in which the transport force F2 of the roller pair 23 is the largest at the position closest to the center C2.

The printer 1 satisfies the above equations (1) and (2). In this case, when the paper 100 is conveyed by the roller pairs 22 and 23 whose surface rollers are spur rollers, skewing can be prevented more reliably.

The printer 1 further satisfies the above equations (3) and (4). In this case, skewing can be prevented even when the paper 100 is conveyed by the rollers 21 and 22.

The rotation speed of the rollers vs. 22 is larger than the rotation speed of the rollers vs. 21, and the transport force of the rollers vs. 21 is larger than the transport force of the rollers vs. 22. In this case, even when the paper 100 is conveyed by the rollers 21 and 22, the transfer can be stabilized.

The roller pair 23 is a roller pair arranged at the most downstream side of the transport path R (see FIG. 1). In this case, even if skew occurs when the paper 100 is conveyed only by the roller pair 23, defects (jams, etc.) due to skew can be suppressed.

The roller pair 23 has a function of imparting a wavy shape along the scanning direction to the paper 100. In this case, from the viewpoint of imparting a wavy shape to the entire width of the paper 100, it is preferable to arrange the roller pair 23 over the entire width of the paper 100, but the conveying force of the roller pair 23 is not constant in the axial direction and is located at the center C2. By making it the largest at the closest position, when the paper 100 is conveyed by the rollers 22 and 23 whose surface rollers are spur rollers, the transfer can be stabilized and skewing can be prevented.

The roller pair 23 is in the same direction as the first outermost position from the center C2 in the axial direction than the first outermost position (positions P1x, P1y) where the roller pair 22 is farthest from the center C1 in the axial direction and holds the paper 100. The second outermost position (positions P2x, P2y) that sandwiches the paper 100 farthest from the center is closer to the centers C1 and C2 in the axial direction (see FIG. 3). In this case, when the paper 100 is conveyed by the roller pairs 22 and 23 in which the surface roller is a spur roller, it becomes easy to satisfy the requirement for stabilizing the transfer and preventing skewing.

The transport force F2 of the roller pair 23 is the smallest in the axial direction of the roller pair 23 at the position farthest from the center C2 (see FIGS. 4 and 5). In this case, by making the transport force F2 of the roller pair 23 the largest at the position closest to the center C2 and the smallest at the position farthest from the center C2, the paper 100 is formed by the roller pairs 22 and 23 whose surface rollers are spur rollers 22 and 23. It is possible to more reliably realize the stabilization of the transportation and the prevention of skewing when the paper is transported.

Although the preferred embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and various design changes can be made as long as it is described in the claims.

<Modification example>
The front surface roller and the back surface roller of the first downstream roller pair and the second downstream roller pair are not limited to being composed of a plurality of partial rollers, and may be composed of one roller elongated in the axial direction. Even in this case, the coefficient of friction and the urging force of the spring change in the axial direction, so that the conveying force may vary in the axial direction.
-The carrying force of the second downstream roller pair in the axial direction is not limited to being adjusted by both the urging force of the urging member provided for each partial roller and the friction coefficient of the outer peripheral surface of the partial roller. It may be adjusted by either the urging force or the coefficient of friction.
-The second downstream roller pair does not have to be arranged at the most downstream of the transport path.
The second downstream roller pair may not have a function of imparting a wave shape along the axial direction to the recording medium (the corrugated spur 23c in the above-described embodiment may be omitted).
-The first outermost position and the second outermost position may coincide with each other in the axial direction.
-The discharge unit is not limited to the serial type and may be a line type.
-The liquid discharged by the ejection unit is not limited to the ink, and may be any liquid (for example, a treatment liquid that aggregates or precipitates the components in the ink).
-The recording medium is not limited to paper, and may be any recordable medium (for example, cloth).
-The present invention is not limited to printers, but can be applied to facsimiles, copiers, multifunction devices, and the like.

1 Printer (liquid discharge device)
20 Transport section 21 Roller pair (upstream roller pair)
21a Front roller 21b Back roller 22 Roller pair (1st downstream roller pair)
22a Surface roller 22a1 Partial roller (1st part roller)
22ap protrusion 22b back surface roller 23 roller pair (second downstream roller pair)
23a Surface roller 23a1 Partial roller (2nd part roller)
23ap protrusion 23as spring (biasing member)
23b Back side roller 30 Discharge part 30 x Discharge port 100 Paper (recording medium)
F0, F1, F2 Conveying force P1x, P1y position (first outermost position)
P2x, P2y position (second outermost position)
R transport route

Claims (11)

A transport unit that transports the recording medium along the transport path,
A discharge unit having a plurality of discharge ports for discharging a liquid on the surface of a recording medium conveyed by the transfer unit is provided.
The transport unit includes an upstream roller pair arranged upstream of the transport path with respect to the discharge unit, a first downstream roller pair arranged downstream of the transport path with respect to the discharge unit, and the first downstream roller pair. Including the second downstream roller pair arranged downstream of the transport path with respect to the downstream roller pair, at the center of each of the upstream roller pair, the first downstream roller pair, and the second downstream roller pair. The recording medium is conveyed by aligning the centers of the recording media in the axial direction.
The upstream roller pair, the first downstream roller pair, and the second downstream roller pair are a front roller that contacts the front surface of the recording medium and a back roller that contacts the back surface of the recording medium that is opposite to the front surface, respectively. The front surface roller and the back surface roller rotate in opposite directions while sandwiching the recording medium, thereby imparting a conveying force to the recording medium to convey the recording medium.
The surface rollers of the first downstream roller pair and the second downstream roller pair are spur rollers having one or more protrusions formed on the outer peripheral surface.
The rotation speed of the second downstream roller pair is larger than the rotation speed of the first downstream roller pair, and the transfer force of the first downstream roller pair is larger than the transfer force of the second downstream roller pair. ,
The surface roller of the second downstream roller pair includes a plurality of second partial rollers separated from each other in the axial direction.
Of the plurality of second partial rollers, the friction coefficient of the outer peripheral surface of the second partial roller arranged at the position closest to the center in the axial direction is higher than the friction coefficient of the outer peripheral surface of the other second partial rollers. big,
A liquid discharge device, characterized in that the conveying force of the second downstream roller pair is not constant in the axial direction of the roller pair, but is greatest at a position closest to the axial center of the roller pair. A transport unit that transports the recording medium along the transport path,
A discharge unit having a plurality of discharge ports for discharging a liquid on the surface of a recording medium conveyed by the transfer unit is provided.
The transport unit includes an upstream roller pair arranged upstream of the transport path with respect to the discharge unit, a first downstream roller pair arranged downstream of the transport path with respect to the discharge unit, and the first downstream roller pair. Including the second downstream roller pair arranged downstream of the transport path with respect to the downstream roller pair, at the center of each of the upstream roller pair, the first downstream roller pair, and the second downstream roller pair. The recording medium is conveyed by aligning the centers of the recording media in the axial direction.
The upstream roller pair, the first downstream roller pair, and the second downstream roller pair are a front roller that contacts the front surface of the recording medium and a back roller that contacts the back surface of the recording medium that is opposite to the front surface, respectively. The front surface roller and the back surface roller rotate in opposite directions while sandwiching the recording medium, thereby imparting a conveying force to the recording medium to convey the recording medium.
The surface rollers of the first downstream roller pair and the second downstream roller pair are spur rollers having one or more protrusions formed on the outer peripheral surface.
The rotation speed of the second downstream roller pair is larger than the rotation speed of the first downstream roller pair, and the transfer force of the first downstream roller pair is larger than the transfer force of the second downstream roller pair. ,
The surface roller of the second downstream roller pair includes a plurality of second partial rollers separated from each other in the axial direction.
Each of the plurality of second portion rollers is further provided with a plurality of urging members for imparting urging forces toward the back surface roller.
Among the plurality of urging members, the urging member provided for the second partial roller arranged at the position closest to the center in the axial direction among the plurality of second partial rollers is the remaining urging member. The urging force is larger than that of the urging member,
A liquid discharge device, characterized in that the conveying force of the second downstream roller pair is not constant in the axial direction of the roller pair, but is greatest at a position closest to the axial center of the roller pair. The transport unit is configured to be capable of transporting recording media of a plurality of sizes.
The distance from the upstream roller pair to the second downstream roller pair along the transport path is not more than or equal to the length along the transport path of the recording medium of one size out of the plurality of sizes. The liquid discharge device according to claim 1 or 2. The liquid discharge device according to any one of claims 1 to 3, wherein the surface roller of the first downstream roller pair includes a plurality of first partial rollers separated from each other in the axial direction. The liquid discharge device according to any one of claims 1 to 4 , wherein the liquid discharge device satisfies the following formulas (1) and (2).
| M1 |> | M2 | (1)
| M1 | / L1 <∫F2 (l) ・ dl (2)
(Here, M1: the moment around the center of the first downstream roller pair in the axial direction caused by the variation in the carrying force of the first downstream roller pair in the axial direction, M2: the said of the second downstream roller pair. Moment around the center of the second downstream roller pair caused by the variation in the transport force in the axial direction, L1: Distance from the first downstream roller pair to the second downstream roller pair along the transport path. , F2 (l): The transport force at each point l in the axial direction of the second downstream roller pair) The liquid discharge device according to claim 5 , further satisfying the following formulas (3) and (4).
｜ M0 ｜＞｜ M1 ｜ (3)
| M0 | / L2 <∫F1 (l) ・ dl (4)
(Here, M0: a moment around the center of the upstream roller pair in the axial direction caused by the variation in the carrying force of the upstream roller pair in the axial direction, L2: from the upstream roller pair to the first downstream roller pair. Distance along the transport path, F1 (l): the transport force at each point l in the axial direction of the first downstream roller pair) The rotation speed of the first downstream roller pair is larger than the rotation speed of the upstream roller pair, and the transport force of the upstream roller pair is larger than the transport force of the first downstream roller pair. The liquid discharge device according to any one of claims 1 to 6. The liquid discharge device according to any one of claims 1 to 7 , wherein the second downstream roller pair is a roller pair arranged at the most downstream of the transport path. The liquid discharge device according to any one of claims 1 to 8 , wherein the second downstream roller pair has a function of imparting a wave shape along the axial direction to the recording medium. The first outermost position of the second downstream roller pair from the center in the axial direction is higher than the first outermost position where the first downstream roller pair sandwiches the recording medium farthest from the center in the axial direction. The second outermost position that sandwiches the recording medium in the same direction as the above is the position closer to the center in the axial direction, according to any one of claims 1 to 9. Liquid discharge device. The liquid according to any one of claims 1 to 10 , wherein the conveying force of the second downstream roller pair is the smallest in the axial direction of the roller pair at a position farthest from the center. Discharge device.

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